1. Field of the Invention
The present invention relates to a roller with a pair of crawlers on both sides of a vehicle body. Furthermore, the present invention relates to a compaction method of the ground of the sloping ground using a roller.
2. Prior Art
As shown in FIG. 12, a vibratory roller 31, in which a vibratory roll 32 is served as the front wheel and a tire T is served as the rear wheel, is conventionally used as one of roller. The roller, such as a vibratory roller, has been used in the compaction of the not steep slope or small uneven ground.
A vibrating shaft 34, which is consists of one axis, and to which the eccentric weight 33 is fixed, is installed within the vibratory roll 32 (herein after defined as the roll). When the vibrating shaft 34 rotates, the roll 32 is vibrated by the eccentric rotation of the vibrating shaft 34, and the vibration force is applied in the 360-degree direction of the periphery of the roll 32, and thus the slope (sloping ground) is compacted.
When the compaction using the vibratory roller 31 is carried out under the disadvantageous condition, such as extremely uneven ground or the muddy land of the construction site of a highway or a dam, arid such as the sloping ground (slope), the operation of the vibratory roller 31 with stableness may be disturbed by the slipping or the sticking of the tire T in the mud. For settling these phenomenon, the applicant of the present patent application discloses the crawler-type vibratory roller for earthwork in the Japanese unexamined patent publication No. 07-3764. According to the disclosed crawler-type vibratory roller, the operation of the vehicle with stableness can be achieved even in the muddy road and the steep sloping ground and the like. The working efficiency thus can be maintained.
When detaching the crawlers from the vehicle body for repairing or replacing, however, the crawlers equipped on both sides of vehicle body are detached separately. The attaching and detaching operation of the crawler thus will be bothered. Furthermore, since the vibratory roller is frequently used in the compaction of the asphalt pavements as well as that of the embankment, it is uneconomical in the traveling efficiency to operate the vibratory roller equipped with the crawler even in the asphalt road surface by which the trafficability is stabilized.
Therefore, the roller, in which the attaching and detaching operation of the crawler is carried out with ease, and the roller which can fully demonstrates the traveling performance depending on the situation of the ground to be compacted, have been required.
In the conventional method for achieving the compaction of the sloping ground using the vibratory roller, the following difficulties have arisen. Generally, a slip of the tire will occur when the driving force at the tread exceeds the shear resistance force of the ground, and in this case the traveling condition becomes unstable.
Therefore, when the vibratory roller climbs a sloping ground, since the inclination of the vehicle body and the jumping of the roll 32, which is caused by the reaction force from the ground, are affected as the compaction progresses, the load applied to the wheel, i.e., a tire T, and the fluctuation thereof are increased. Consequently, the slip of the tire occurs via the jumping of the roll 32 and the inclination of the vehicle body, and then the vehicle body tends to become unstable.
Specifically, according to the vibratory mechanism of the roll 32, since the vibration force is applied to the roll 32 along the 360-degree direction of the periphery by the rotation of the eccentric weight 33, the roll 32 is vibrated.
The measurement value of the wave profile in the ups-and-downs and front-and-rear directions to the vehicle of the vibration acceleration, which is applied to the roll 32, is shown in FIG. 13A. The wave composite of the vibration acceleration is shown in FIG. 13B. As can be seen from FIG. 13D, the wave composite of the vibration acceleration is displacing and rotating along the ellipse-shaped locus centering on the axial center of the roll 32. According to this wave composite, since the reaction force is applied in all directions from the cross direction to the perpendicular direction at the tread, the vehicle body inclining at the sloping ground tends to become unstable.
When the component in the front-and-rear directions of the vibration force of the roll 32 is slightly deviated from the center (center of gravity) in the longitudinal direction of the vibratory roller 31, the vibration force is given to the vibratory roller 31 as a moment. Thus, the steering of the vibratory roller 31 becomes difficult.
The degree of the unstableness of the roll 32 is further increased by the slight unbalance of the weight in the longitudinal direction of the roll 32, the slight difference in the rigidity of vibration proof rubbers of left side and right side (not shown) between which the roll 32 is supported, and the difference of the reaction force from the ground which is affected by the soil and the shape of the ground. As a result of these unstableness, the jumping of the roll 32 will be promoted.
In the compaction of the sloping ground, particularly, since the direction of the center of gravity of the vehicle body (the gravity direction) is not perpendicular with respect to the slope surface, when the load fluctuation to the tire T and the slip phenomenon of the tire T are coupled thereto, the degree of the unstableness of the vehicle body is increased. Thus, the operationablity of the steering wheel becomes difficult and then the keeping of the attitude of the vehicle body becomes difficult.
Therefore, there has been required that the vibratory roller, which can compact the ground on stabilizing the vehicle body even in tie steep sloping ground, and the compaction method of the sloping ground using the vibratory roller.